This invention relates to methods of producing laminated polyolefin films by coextrusion and laminated polyolefin films produced by coextrusion.
Laminated polyolefin films produced by coextrusion are coming to be used widely as food packaging and agricultural materials. Depending upon their intended use, such laminated polyolefin films are required not only to be transparent but also to have both antistatic and antifogging properties at the same time, and demands for improving these properties are becoming severe in recent years. The present invention relates to methods of producing laminated polyolefin films by coextrusion and laminated polyolefin films produced by coextrusion with which such demands can be met.
Prior art examples of compounds and compositions for providing antistatic and antifogging properties to laminated polyolefin films as they are being produced by coextrusion include (1) glyceride (Japanese Patent Publication Tokkai 63-173640), (2) betaines, polyoxyethylene alkylamines and polyoxyethylene alkylamine fatty acid esters (Japanese Patent Publication Tokkai 7-251445), (3) esters of polyhydric alcohol and fatty acid and hydroxyalkyl substituted aliphatic amines (Japanese Patent Publication Tokkai 10-80985), (4) ethylene oxide adduct of betaines, quaternary ammonium salts and glycerol aliphatic acid esters (Japanese Patent Publication Tokkai 11-115124), and (5) hydroxyalkyl substituted fatty acid amides, polyoxyethylene alkylamines and polyoxyethylene alkylamides (Japanese Patent Publication Tokkai 11-240115). These prior art compounds and compositions have the problem that they cannot provide superior and durable antistatic and antifogging properties to a laminated polyolefin film without adversely affecting its natural transparency.